Debug templates

I did (a lot) of customization to the apache plugin and vhost.conf.master to better integrate ISPConfig in our network.
Now the server.php isn't able to finish properly due to an issue in the vhost.conf.master template.
How can I enable the debug for this ?
vLibTemplate is saying this:

vlibTemplate Error: Parse error!<br>To debug this file, use vlibTemplateDebug instead of vlibTemplate in the class instantiation(i.e. new vlibTemplateDebug).

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but I don't know where to call vlibTemplateDebug, there is no vlibTemplate instantiation in ISPConfig 3.0.5, AFAIK the class is used as standalone in "tpl.inc.php"